From HcPro’s monthly newsletter Briefings on HIPAA:
Q: When a physician from our office refers a patient to a specialist, is a signed medical release from the patient necessary to send records to the specialist? Also, may we send copies of the patient’s records from a prior treating physician that the patient provided?
A: The HIPAA privacy rule permits covered entities to disclose PHI without patient authorization for treatment, payment, and healthcare operations. This is clearly a treatment situation, so patient authorization is unnecessary.
In addition, the “minimum necessary” requirement does not apply to treatment disclosures, so you may send the specialist whatever information you think would be helpful in evaluating the patient, including copies of records from physicians who previously treated the patient.